This invention relates generally to a method of making carbon nanoporous materials and, more particularly, to a method of synthesizing nanoporous carbon nanotubes, nanoparticles, and films from a precursor solution comprising block copolymers and carbohydrates.
Carbon nanoporous materials, including nanoporous thin films, nanotubes, and nanoparticles, have received great attention due to their unique optical, electrical, and mechanical properties and their potential applications in nanoelectronics, sorption, and gas sensor applications. Various indirect and direct methods have been developed for the synthesis of carbon nanomaterials. For example, mesoporous carbon films have been synthesized through high temperature pyrolysis of mixtures of poly(ethylene glycol) (PEG) and poly(furfuryl alcohol). Removal of PEG during pyrolysis process led to disordered porous films with less controlled pore structure and limited accessibility and porosity. One indirect method synthesizes mesoporous carbon films with a disordered pore structure, where sucrose/silica nanocomposite films were first synthesized, followed by carbonization art high temperature and hydrogen fluoroacid etching, leading to disordered mesoporous carbon films. Through surfactant and polymer templating process, ordered mesoporous carbon films with 1-dimensional pore channels and hexagonal mesostructure have been synthesized. However, their thin film mesopore accessibility has not been demonstrated yet. In addition, the one-dimensional pore channels limit their applications where as 3-dimensional pore structures are preferred for transport.
Methods for synthesis of nanotubes have included dc arc-discharge, laser ablation, and chemical vapor deposition techniques. Recently templating methods have been developed to synthesize carbon nanotubes by carbonization of either polymer or pre-organized disc-like molecules in porous anodic aluminum oxide (AAO) membranes. In general, the carbon nanotubes synthesized using these methods exhibit either graphite-structured or amorphous tube walls with microporosity (pore size<0.5 nm). In many applications such as macromolecule sorption, separation, and sensing, carbon nanotubes with larger pores are preferred. One method synthesized hollow carbon tubes with randomly distributed 4-nm pore on the tube wall and rectangular-shape channels using mesoporous silica tubes as templates. However, this method has several limitations, including the difficulty in synthesizing tubular silica templates, controlling the tube diameter, length, and pore size on the wall and the problem of infiltrating carbon precursors into the templates which relies on capillary forces that can't guarantee complete filling of the mesopore and the entire silica tube wall. Thus, after removal of silica templates, some of the resulting carbon tubes have un-connected pores and irregular shapes. Additionally, pore size control of mesoporous carbon synthesized using silica templates is very limited because the wall thickness control of silica templates is very difficult. Generally, the pore diameter of mesoporous carbons is less than 5-nm.